In an adipose tissue-specific KLB transgenic mouse, the maintenance of KLB protein expression in WAT does not alleviate the impairment in FGF21 signaling associated with obesity, thus indicating that the KLB expression downregulation may not be the major mechanism contributing to impaired FGF21 signaling in WAT [166]. The gene discussed is FGF21; the disease is obesity due to melanocortin 4 receptor deficiency.